Conventionally, among a technology for producing metal foil by a continuous electrolysis method, production of an electro-deposited copper foil that is a basic material for producing a printed-wiring board has been a typical technology. For example, in the apparatus for a continuous electrolysis of electro-deposited copper foil, a drum (cylindrical) cathode and an anode such as a lead alloy electrode made of an insoluble lead-silver alloy or the like.
The lead alloy electrode is acid resistant against to an acidic metal salt solution with high concentration such as a copper sulfate solution. Also, because the lead alloy electrode is composed of lead having a low melting point, it makes forming of a curving shape on anode surface to be faced along a shape of a surface of a drum cathode easy and also makes working at an installation site of an electrolysis apparatus. That is, the lead alloy electrode has been widely used because of excellent material workability which enables high operability.
However, with increasing size of the continuous electrolysis apparatus, it has been made difficult to obtain a uniform alloy composition in the same surface of the lead alloy electrode. Also, for the lead alloy electrode in a sulfuric acid base solution used as an electrolytic solution, deviations in alloy composition, a difference in crystal structure and the like between lots drastically affect polarization performance in electrolysis, and it has been made difficult to produce electro-deposited copper foil having high quality in an advanced technologies.
In addition, the lead alloy electrode is consumed in electrolysis to result deformation of a shape of an electrode surface easily, and maintenance costs are increased. Further, a lead component discharged according to the consumption of electrode into the electrolytic solution may form substances such as metal lead, lead ion, lead sulfate, or lead oxide. They may cause various defects in products when contaminated in the electro-deposited copper foil.
Thus, Japanese Patent Laid-Open No. 5-202498 discloses “an insoluble electrode structure in which a thin sheet insoluble metal electrode provided with a conductive electrode material which is mounted on at least a part of an electrolysis-side surface of a plate-like or curved electrode base is made detachable by mounting means such as a screw, and a surface of the electrode base in contact with the thin plate insoluble electrode is coated with a conductive electrode material.” As is apparent from FIG. 1 disclosed in Japanese Patent Laid-Open No. 5-202498, the insoluble electrode structure that can be used as a production apparatus of electro-deposited copper foil is disclosed. The insoluble electrode structure has been a solution of the problems that occur in using of the above-described lead alloy electrode, and has increased production stability of the electro-deposited metal foil.    Patent Document 1: Japanese Patent Laid-Open No. 5-202498
However, even when the insoluble electrode structure disclosed in Japanese Patent Laid-Open No. 5-202498 is used in continuous production of electro-deposited metal foil; it could not always satisfy latest requirements for electro-deposited metal foil.
In particular, there arises a sincere requirement to reduce thickness fluctuation of electro-deposited copper foil. That is, for the electro-deposited copper foil, thinner electro-deposited copper foil with less thickness fluctuation has been required in terms of improvement in formation of a fine pitch circuit on a printed-wiring board produced by using the electro-deposited copper foil, working accuracy in thickness reduction of a multilayer printed-wiring board, and downsizing.
Thus, there has been a requirement for a production apparatus for electro-deposited metal foil that can reduce thickness fluctuation of electro-deposited metal foil such as electro-deposited copper foil, and an electro-deposited metal foil with less thickness fluctuation produced by using the production apparatus for electro-deposited metal foil.